The present invention relates generally to dense wavelength division multiplexing networks and, more particularly, to an optical power managed network node for processing dense wavelength division multiplexed optical signals.
Dense wavelength division multiplexing (DWDM) networks typically comprise a plurality of network nodes for receiving and transmitting dense wavelength division multiplexed optical signals. Each of the plurality of network nodes typically allows an individual optical signal that is contained in a received dense wavelength division multiplexed optical signal to either simply pass through the network node and then be transmitted further along the network from the network node, or be xe2x80x9cdroppedxe2x80x9d at the network node for use by one or more sub-nodes connected to the network node. Each of the plurality of network nodes also typically allows one or more individual optical signals to be xe2x80x9caddedxe2x80x9d to the network at the network node. These xe2x80x9caddedxe2x80x9d optical signals are typically transmitted further along the network from the network node along with other optical signals that are received at the network node, but are not xe2x80x9cdroppedxe2x80x9d at the network node. The above-described network node is generally referred to as an optical add/drop network node due to the xe2x80x9caddingxe2x80x9d and xe2x80x9cdroppingxe2x80x9d functions performed by the network node.
The xe2x80x9caddingxe2x80x9d and xe2x80x9cdroppingxe2x80x9d functions performed by most existing optical add/drop network nodes typically result in a difference between the power of a dense wavelength division multiplexed optical signal that is received at the optical add/drop network node and the power of a dense wavelength division multiplexed optical signal that is transmitted from the optical add/drop network node. For example, if more optical signals are xe2x80x9cdroppedxe2x80x9d at the optical add/drop network node than are xe2x80x9caddedxe2x80x9d at the optical add/drop network node, then the power of the dense wavelength division multiplexed optical signal that is received at the optical add/drop network node will typically be more than the power of the dense wavelength division multiplexed optical signal that is transmitted from the optical add/drop network node.
Also, most existing optical add/drop network nodes typically inflict some degree of loss upon the power of the optical signals that are received at each network node. That is, an optical add/drop network node typically receives a dense wavelength division multiplexed optical signal in multiplexed form, and then demultiplexes the received dense wavelength division multiplexed optical signal in order for the individual optical signals that are contained within the received dense wavelength division multiplexed optical signal to be processed by the optical add/drop network node. Also, the processing of the individual optical signals at an optical add/drop network node typically comprises switching the individual optical signals such that the individual optical signals are either passed through the optical add/drop network node or xe2x80x9cdroppedxe2x80x9d at the optical add/drop network node. Further, the individual optical signals that are passed through the optical add/drop network node are recombined (i.e., multiplexed) prior to being transmitted further along the network from the optical add/drop network node. All of the above-described demultiplexing, switching, and multiplexing functions typically inflict some degree of loss upon the power of the optical signals that are received at the optical add/drop network node.
The above-described multiplexing function losses that are inflicted upon the power of the optical signals that are received at the optical add/drop network node are also typically inflicted upon the power of any optical signals that are xe2x80x9caddedxe2x80x9d to the network at the optical add/drop network node. That is, optical signals that are xe2x80x9caddedxe2x80x9d to the network at the optical add/drop network node are combined (i.e., multiplexed) with optical signals that are otherwise received at the optical add/drop network node, and a resulting dense wavelength division multiplexed optical signal is transmitted further along the network from the optical add/drop network node. Thus, optical signals that are xe2x80x9caddedxe2x80x9d to the network at the optical add/drop network node are also typically subject to multiplexing function losses.
Furthermore, optical signals that are xe2x80x9caddedxe2x80x9d to a network at most existing optical add/drop network nodes typically have a power level that is different from the optical signals that are otherwise received at the optical add/drop network node. This difference in power between xe2x80x9caddedxe2x80x9d optical signals and optical signals that are otherwise received at the optical add/drop network node typically effects the power of the resulting dense wavelength division multiplexed optical signal that is transmitted further along the network from the optical add/drop network node. For example, if the power of xe2x80x9caddedxe2x80x9d optical signals is greater than the power of optical signals that are otherwise received at the optical add/drop network node, then the power of the resulting dense wavelength division multiplexed optical signal that is transmitted further along the network from the optical add/drop network node is typically greater than the power of the dense wavelength division multiplexed optical signal that is initially received at the optical add/drop network node.
Additionally, differences in power between xe2x80x9caddedxe2x80x9d optical signals and optical signals that are otherwise received at most existing optical add/drop network nodes can cause problems such as, for example, channel crosstalk, in the resulting dense wavelength division multiplexed optical signal that is transmitted further along the network from the optical add/drop network node. That is, when xe2x80x9caddedxe2x80x9d optical signals are combined (i.e., multiplexed) with optical signals that are otherwise received at the optical add/drop network node, the higher power optical signals often interfere with the lower power optical signals.
All of the above-described power related problems associated with existing optical add/drop network nodes require an operator of a network to continually perform some type of manual network initialization procedure whenever additional optical signals are added to the network, existing optical signals are dropped from the network, or the network is otherwise reconfigured in some manner (e.g., an additional optical add/drop network node is added to the network, an existing optical add/drop network node is removed from the network, etc.). That is, a network operator typically has to perform such a manual network initialization procedure whenever a change occurs in the network such that there is a corresponding change in the power of a dense wavelength division multiplexed optical signal that is transmitted from an optical add/drop network node. Such a change in the power of a dense wavelength division multiplexed optical signal that is transmitted from an optical add/drop network node is seen at every subsequent optical add/drop network node that receives this same dense wavelength division multiplexed optical signal either directly or after all or a portion of this same dense wavelength division multiplexed optical signal propagates through one or more subsequent optical add/drop network nodes. Thus, a network operator typically has to perform a manual network initialization procedure on most, if not all, optical add/drop network nodes in the network so that these optical add/drop network nodes can accommodate the change in the power of every received dense wavelength division multiplexed optical signal.
Obviously, the above-described manual network initialization procedure can be costly in terms of both time spent by a network operator and the cost of optical power measurement and adjustment equipment. Thus, it would be desirable to provide a technique for overcoming the above-described inadequacies and shortcomings of existing optical add/drop network nodes. More particularly, it would be desirable to provide an optical power managed network node for processing dense wavelength division multiplexed optical signals in an efficient and cost effective manner.
The primary object of the present invention is to provide an optical power managed network node for processing dense wavelength division multiplexed optical signals in an efficient and cost effective manner.
The above-stated primary object, as well as other objects, features, and advantages, of the present invention will become readily apparent to those of ordinary skill in the art from the following summary and detailed descriptions, as well as the appended drawings. While the present invention is described below with reference to preferred embodiment(s), it should be understood that the present invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present invention as disclosed and claimed herein, and with respect to which the present invention could be of significant utility.
According to the present invention, a technique for processing dense wavelength division multiplexed signals in a network node is provided. In one exemplary embodiment, the technique is realized as an optical power managed network node comprising a demultiplexing device for separating a first multiplexed polychromatic optical signal into a first plurality of narrowband optical signals. The optical power managed network node also comprises a switching device for switching the first plurality of narrowband optical signals according to a predetermined signal routing scheme so as to generate a second plurality of narrowband optical signals. The optical power managed network node further comprises a plurality of attenuators for attenuating the power of at least one of the second plurality of narrowband optical signals so as to generate a plurality of attenuated narrowband optical signals, wherein the power of the at least one of the second plurality of narrowband optical signals is attenuated based upon a power level of each of the plurality of attenuated narrowband optical signals. The optical power managed network node still further comprises a dense wavelength division multiplexing device for combining the plurality of attenuated narrowband optical signals into a second multiplexed polychromatic optical signal. The optical power managed network node additionally comprises a wavelength-selective optical power detector for detecting the power level of each of the plurality of attenuated narrowband optical signals combined into the second multiplexed polychromatic optical signal.
In accordance with other aspects of this exemplary embodiment of the present invention, the at least one of the second plurality of narrowband optical signals is beneficially attenuated so as to equalize the power in each of the second plurality of narrowband optical signals.
In accordance with further aspects of this exemplary embodiment of the present invention, the optical power managed network node further beneficially comprises an adjustable power amplifier for adjustably amplifying the power of the second multiplexed polychromatic optical signal based upon the detected power level of each of the plurality of attenuated narrowband optical signals.
In accordance with still further aspects of this exemplary embodiment of the present invention, the second plurality of narrowband optical signals comprises at least a portion of the first plurality of narrowband optical signals. That is, at least one of the first plurality of narrowband optical signals may beneficially be switched such that the at least one switched narrowband optical signal is routed through the optical power managed network node. Also, at least one other of the first plurality of narrowband optical signals may beneficially be switched such that the at least one switched narrowband optical signal is routed to a local sub-node. Further, the switching device may beneficially receive at least one of a third plurality of narrowband optical signals for routing through the optical power managed network node. Thus, the second plurality of narrowband optical signals comprises those of the first plurality of narrowband optical signals and the third plurality of narrowband optical signals that are routed through the optical power managed network node. It should be noted that the optical power managed network node may further beneficially comprise a controller for controlling the power of the at least one of the third plurality of narrowband optical signals based upon the detected power level of each of the plurality of attenuated narrowband optical signals.
In accordance with still further aspects of this exemplary embodiment of the present invention, the wavelength-selective optical power detector also beneficially detects the power level of each of the first plurality of narrowband optical signals contained within the first multiplexed polychromatic optical signal. Alternatively, wherein the wavelength-selective optical power detector is a first wavelength-selective optical power detector, the optical power managed network node may further beneficially comprise a second wavelength-selective optical power detector for detecting the power level of each of the first plurality of narrowband optical signals contained within the first multiplexed polychromatic optical signal.
In another exemplary embodiment, the technique is realized as a method for processing dense wavelength division multiplexed signals in an optical power managed network node. The method comprises separating a first multiplexed polychromatic optical signal into a first plurality of narrowband optical signals. The method also comprises switching the first plurality of narrowband optical signals according to a predetermined signal routing scheme so as to generate a second plurality of narrowband optical signals. The method further comprises attenuating the power of at least one of the second plurality of narrowband optical signals so as to generate a plurality of attenuated narrowband optical signals, wherein the power of the at least one of the second plurality of narrowband optical signals is attenuated based upon a power level of each of the plurality of attenuated narrowband optical signals. The method still further comprises combining the plurality of attenuated narrowband optical signals into a second multiplexed polychromatic optical signal. The method additionally comprises detecting the power level of each of the plurality of attenuated narrowband optical signals combined into the second multiplexed polychromatic optical signal.
In accordance with other aspects of this exemplary embodiment of the present invention, the at least one of the second plurality of narrowband optical signals is beneficially attenuated so as to equalize the power in each of the second plurality of narrowband optical signals.
In accordance with further aspects of this exemplary embodiment of the present invention, the power of the second multiplexed polychromatic optical signal is beneficially adjustably amplified based upon the detected power level of each of the plurality of attenuated narrowband optical signals.
In accordance with still further aspects of this exemplary embodiment of the present invention, the second plurality of narrowband optical signals comprises at least a portion of the first plurality of narrowband optical signals. That is, at least one of the first plurality of narrowband optical signals may beneficially be switched such that the at least one switched narrowband optical signal is routed through the optical power managed network node. Also, at least one of the first plurality of narrowband optical signals may beneficially be switched such that the at least one switched narrowband optical signal is routed to a local sub-node. Further, at least one of a third plurality of narrowband optical signals may beneficially be received for routing through the optical power managed network node. Thus, the second plurality of narrowband optical signals comprises those of the first plurality of narrowband optical signals and the third plurality of narrowband optical signals that are routed through the optical power managed network node. It should be noted that the power of the at least one of the third plurality of narrowband optical signals may be beneficially controlled based upon the detected power level of each of the plurality of attenuated narrowband optical signals.
In accordance with still further aspects of this exemplary embodiment of the present invention, the power level of each of the first plurality of narrowband optical signals contained within the first multiplexed polychromatic optical signal may beneficially be detected along with the power level of each of the plurality of attenuated narrowband optical signals combined into the second multiplexed polychromatic optical signal. Alternatively, the power level of each of the first plurality of narrowband optical signals contained within the first multiplexed polychromatic optical signal may beneficially be detected separately from the power level of each of the plurality of attenuated narrowband optical signals combined into the second multiplexed polychromatic optical signal.
In still another exemplary embodiment, the technique is realized as an optical power managed network node comprising a demultiplexing device for separating a first multiplexed polychromatic optical signal into a first plurality of narrowband optical signals. The optical power managed network node also comprises a switching device for switching the first plurality of narrowband optical signals and a third plurality of narrowband optical signals according to a predetermined signal routing scheme so as to generate a second plurality of narrowband optical signals. The optical power managed network node further comprises a plurality of attenuators for attenuating the power of at least one of the second plurality of narrowband optical signals so as to generate a plurality of attenuated narrowband optical signals, wherein the power of the at least one of the second plurality of narrowband optical signals is attenuated based upon a power level of each of the plurality of attenuated narrowband optical signals. The optical power managed network node still further comprises a dense wavelength division multiplexing device for combining the plurality of attenuated narrowband optical signals into a second multiplexed polychromatic optical signal. The optical power managed network node still further comprises an adjustable power amplifier for adjustably amplifying the power of the second multiplexed polychromatic optical signal so as to generate an amplified multiplexed polychromatic optical signal containing the plurality of attenuated narrowband optical signals, wherein the power of the second multiplexed polychromatic optical signal is adjustably amplified based upon the power level of each of the plurality of attenuated narrowband optical signals. The optical power managed network node still further comprises a wavelength-selective optical power detector for detecting the power level of each of the plurality of attenuated narrowband optical signals contained in the amplified multiplexed polychromatic optical signal, and for detecting the power level of each of the first plurality of narrowband optical signals contained within the first multiplexed polychromatic optical signal. The optical power managed network node additionally comprises a controller for controlling the power attenuation of the at least one of the second plurality of narrowband optical signals and the power of at least one of the third plurality of narrowband optical signals based upon the detected power level of each of the plurality of attenuated narrowband optical signals.